diff --git a/examples/plug_app/lib/plug_app/user_handler.ex b/examples/plug_app/lib/plug_app/user_handler.ex
index 8a598245..50061033 100644
--- a/examples/plug_app/lib/plug_app/user_handler.ex
+++ b/examples/plug_app/lib/plug_app/user_handler.ex
@@ -58,7 +58,31 @@ defmodule PlugApp.UserHandler do
         description: "Show a user by ID",
         operationId: "UserHandler.Show",
         parameters: [
-          parameter(:id, :path, %Schema{type: :integer, minimum: 1}, "User ID", example: 123)
+          parameter(:id, :path, %Schema{type: :integer, minimum: 1}, "User ID", example: 123),
+          parameter(:qux, :query, %Schema{type: :string}, "qux param", required: false),
+          parameter(
+            :some,
+            :query,
+            %Schema{
+              type: :object,
+              oneOf: [
+                %Schema{
+                  type: :object,
+                  properties: %{foo: %Schema{type: :string}, bar: %Schema{type: :string}},
+                  required: [:foo]
+                },
+                %Schema{
+                  type: :object,
+                  properties: %{foo: %Schema{type: :string}, baz: %Schema{type: :string}},
+                  required: [:baz]
+                }
+              ]
+            },
+            "Some query parameter ",
+            explode: true,
+            style: :form,
+            required: true
+          )
         ],
         responses: %{
           200 => response("User", "application/json", Schemas.UserResponse)
@@ -80,6 +104,8 @@ defmodule PlugApp.UserHandler do
     end
 
     def show(conn = %Plug.Conn{assigns: %{user: user}}, _opts) do
+      user = Accounts.get_user!(conn.params.id)
+
       conn
       |> put_resp_header("content-type", "application/json")
       |> send_resp(200, render(user))
diff --git a/examples/plug_app/test/user_handler_test.exs b/examples/plug_app/test/user_handler_test.exs
index 50866244..6774f0da 100644
--- a/examples/plug_app/test/user_handler_test.exs
+++ b/examples/plug_app/test/user_handler_test.exs
@@ -46,7 +46,7 @@ defmodule UserHandlerTest do
     } do
       %{resp_body: body} =
         conn =
-        conn(:get, "/api/users/#{user_id}")
+        conn(:get, "/api/users/#{user_id}?foo=asd")
         |> Router.call(@opts)
 
       assert %{status: 200} = conn
@@ -57,6 +57,25 @@ defmodule UserHandlerTest do
 
       assert_schema(json_response, "UserResponse", api_spec)
     end
+
+    test "responds with 422 when there is no either foo nor bar in query params", %{
+      user: %{id: user_id},
+      api_spec: _api_spec
+    } do
+      %{resp_body: body} =
+        conn =
+        conn(:get, "/api/users/#{user_id}")
+        |> Router.call(@opts)
+
+      assert %{status: 422} = conn
+
+      json_response = Jason.decode!(body)
+
+      IO.inspect(json_response)
+      # assert %{} = json_response
+
+      # assert_schema(json_response, "UserResponse", api_spec)
+    end
   end
 
   describe "POST /api/users" do
diff --git a/lib/open_api_spex/cast_parameters.ex b/lib/open_api_spex/cast_parameters.ex
index 1155cb79..1b4285b1 100644
--- a/lib/open_api_spex/cast_parameters.ex
+++ b/lib/open_api_spex/cast_parameters.ex
@@ -74,6 +74,7 @@ defmodule OpenApiSpex.CastParameters do
     }
   end
 
+
   # Extract context information from parameters, useful later when casting
   defp parameters_contexts(parameters) do
     Map.new(parameters, fn parameter ->
@@ -127,6 +128,7 @@ defmodule OpenApiSpex.CastParameters do
       location,
       schema.properties |> Map.keys() |> Enum.map(&Atom.to_string/1)
     )
+    |> maybe_combine_params(schema, parameters_contexts)
     |> pre_parse_parameters(parameters_contexts, parsers)
     |> case do
       {:error, _} = err -> err
@@ -134,6 +136,60 @@ defmodule OpenApiSpex.CastParameters do
     end
   end
 
+  # in caase some parameters have explode: true we want to search for those
+  # fields in parameters and combine the parameters in a single struct
+  # so that the casting can do further work
+  defp maybe_combine_params(%{} = parameters, %{} = schema, %{} = parameters_contexts) do
+    # first filter out from parameters fields that match non exploding properties.
+    # we do this because we want to keep the original parameters struct intact
+    # and not remove fields that are not part of the exploding property
+
+    non_exploding_matches =  Enum.reduce(parameters, Map.new(), fn {key, value}, acc ->
+      case Map.get(parameters_contexts, key, %{}) do
+        %{explode: false} ->
+          Map.put(acc, key, value)
+
+        _ ->
+          acc
+      end
+    end)
+
+    possible_exploding_matches = Enum.reject(parameters, &Enum.member?(non_exploding_matches, &1)) |> Map.new()
+
+    combined_params = Enum.reduce(parameters_contexts, possible_exploding_matches, fn
+      {key, %{explode: true}}, parameters ->
+        # we have exploding property, we need to search for it's possible fields
+        # and add them under the key into the parameters struct.
+        #  do we leave the fields in the params as well? not sure.
+        schema_of_exploding_property = Map.get(schema.properties, String.to_existing_atom(key), %{})
+
+        fields =
+          Schema.properties(schema_of_exploding_property) ++
+            Schema.possible_properties(schema_of_exploding_property)
+
+        {struct_params, found_keys} =
+          Enum.reduce(fields, {Map.new(), []}, fn {field_key, _default}, {struct_params, found_keys} ->
+            param_field_key = field_key |> Atom.to_string()
+            val = Map.get(parameters, param_field_key)
+
+              unless is_nil(val) do
+                {Map.put(struct_params, param_field_key, val), [param_field_key | found_keys]}
+              else
+                {struct_params, found_keys}
+              end
+          end)
+
+        parameters
+        |> Map.drop(found_keys)
+        |> Map.put(key, struct_params)
+
+      _, parameters ->
+        parameters
+    end)
+
+    Map.merge(non_exploding_matches, combined_params)
+  end
+
   defp pre_parse_parameters(%{} = parameters, %{} = parameters_context, parsers) do
     Enum.reduce_while(parameters, Map.new(), fn {key, value}, acc ->
       case pre_parse_parameter(value, Map.get(parameters_context, key, %{}), parsers) do
diff --git a/lib/open_api_spex/schema.ex b/lib/open_api_spex/schema.ex
index a608a85f..096d180a 100644
--- a/lib/open_api_spex/schema.ex
+++ b/lib/open_api_spex/schema.ex
@@ -344,6 +344,23 @@ defmodule OpenApiSpex.Schema do
 
   def properties(_), do: []
 
+  @doc """
+  Get the names of all properties possible for polymorphic schemas using `oneOf`.
+
+  This is different from properties/1 in that it returns properties that *might*
+  be a part of the schema sometimes based on the discriminator.
+  """
+
+  def possible_properties(%Schema{oneOf: schemas}) when is_list(schemas) do
+    Enum.flat_map(schemas, &properties/1) |> Enum.uniq()
+  end
+
+  def possible_properties(%Schema{anyOf: schemas}) when is_list(schemas) do
+    Enum.flat_map(schemas, &properties/1) |> Enum.uniq()
+  end
+
+  def possible_properties(_), do: []
+
   @doc """
   Generate example value from a `%Schema{}` struct.
 
diff --git a/test/cast_parameters_test.exs b/test/cast_parameters_test.exs
index b881a914..fb250e05 100644
--- a/test/cast_parameters_test.exs
+++ b/test/cast_parameters_test.exs
@@ -191,6 +191,20 @@ defmodule OpenApiSpex.CastParametersTest do
               [%OpenApiSpex.Cast.Error{format: "application/json", reason: :invalid_format}]} =
                CastParameters.cast(conn, operation, spec)
     end
+
+    test "cast param with oneof and valid args" do
+      {operation, spec} = oneof_query_spec_operation()
+
+      filter_params = URI.encode_query(%{size: "XL"})
+
+      conn =
+        :get
+        |> Plug.Test.conn("/api/users?#{filter_params}")
+        |> Plug.Conn.put_req_header("content-type", "application/json")
+        |> Plug.Conn.fetch_query_params()
+
+      assert {:ok, _} = CastParameters.cast(conn, operation, spec)
+    end
   end
 
   defp create_conn() do
@@ -294,4 +308,54 @@ defmodule OpenApiSpex.CastParametersTest do
 
     {operation, spec}
   end
+
+  defp oneof_query_spec_operation() do
+    schema = %Schema{
+      type: :object,
+      title: "Filters",
+      oneOf: [
+        %Schema{
+          type: :object,
+          properties: %{
+            size: %Schema{type: :string, pattern: "^XS|S|M|L|XL$"},
+            color: %Schema{type: :string}
+          },
+          required: [:size]
+        },
+        %Schema{
+          type: :object,
+          properties: %{
+            size: %Schema{type: :string, pattern: "^XS|S|M|L|XL$"},
+            color: %Schema{type: :string}
+          },
+          required: [:color]
+        }
+      ],
+      example: %{size: "XL"}
+    }
+
+    parameter = %Parameter{
+      in: :query,
+      name: :filter,
+      required: false,
+      schema: %Reference{"$ref": "#/components/schemas/Filters"},
+      explode: true,
+      style: :form,
+      required: true
+    }
+
+    operation = %Operation{
+      parameters: [parameter],
+      responses: %{
+        200 => %Schema{type: :object}
+      }
+    }
+
+    spec =
+      spec_with_components(%Components{
+        schemas: %{"Filters" => schema}
+      })
+
+    {operation, spec}
+  end
 end